Preparation of fluorescent thermal transfer ribbon

ABSTRACT

A method for the preparation of a fluorescent ink layer for a fluorescent thermal transfer sheet is disclosed. The method comprises first forming a solution of a mixture comprising at least one acidic monomer, at least one basic monomer and at least one fluorescent dye. Thereafter, an emulsion of the solution is formed and the emulsion is polymerized.

This application is a division of Ser. No. 06/818,937 filed 01/15/87,now U.S. Pat. No. 4,657,697.

BACKGROUND OF THE DISCLOSURE

I. Field of the Invention

This invention is concerned with a ribbon or tape for use in non-impactprinting, and more particularly, to a method for the preparation of afluorescent ink coating that is applied to a ribbon to make afluorescent thermal transfer ribbon. The method by which the fluorescentink coating is made is a monomer polymerization method.

II. Description of the Prior Art

It is known in prior art to use ribbons in thermal transfer imagingprocesses. In these processes, thermal means are used to selectivelyheat areas of ribbon having an image transfer layer or coating. Theprinting is generally achieved by heat transferring the coating from theribbon to paper by the local heating of the ribbon. Such image-localizedheating may be accomplished by contacting the ribbon with pointelectrodes or some sort of heating element and a broad area contactelectrode or heating element. The high current densities in the area ofthe electrodes during the application of the applied voltage producesintense local heating which causes transfer of the coating frrom theribbon to either paper or any receiving medium adjacent to or in contactwith the ribbon. Various publications such as IBM Technical DisclosureBulletin entitled "Resistive Ribbon Thermal Transfer Printing Method",Crooks, et al., vol. 19, No. 11, April, 1977, p. 4396 illustrate thisgeneral thermal transfer technique. Printers and various other hardwareused in these methods are disclosed in, for example, U.S. Pat. Nos.4,326,812; 4,327,365 and 4,329,071.

The ink and substrate are basically the keys to a thermal transfertechnique. Various known prior art substrates have been used includingMylar, condenser paper, other polyesters and conductive polyurethanes.Of these, two substrates are most commonly used, i.e., Mylar and specialcondenser paper. Mylar is a registered trademark of DuPont. Thepreferred Mylar ranges in thickness from about 3.5 to 6 microns and thespecial condenser paper ranges in thickness from about 10 to 13 microns.Condenser paper is used in thermal line printers in widths ranging fromabout 33 to 267 mm. (The low tear strength of the condenser paperprecludes its use for narrower ribbons.) Polyester film like Mylar isfound in thermal serial printers in common widths of about 6.35, 8.0 and12.7 mm. The length of both condenser paper and polyester film dependsupon the space available in the printer or ribbon cassettes. There areother substrates known to be adapted for use in thermal transfer ribbonssuch as those are described in U.S. Pat. Nos. 4,103,066, 4,269,892,4,291,994 and 4,320,170.

In the machine processing of various types of information contained ontickets, tags, labels, postage imprints and the like, it is generallyknown to employ detectors which are responsive to shape relationshipsand/or colors, and in many cases to the fluorescence of an ink which maybe excited, for example, by ultraviolet light. Fluorescent inks and dyeshave long been known such as, for example, those disclosed in U.S. Pat.Nos. 2,681,317, 2,763,785, 3,230,221, 3,412,104, 3,452,075, and3,560,238. The fluorescent inks and the methods of making or using themas known in the prior art, generally entail the use of a fluorescent inkwhich, when irradiated, will fluoresce and emit radiation within thewavelength for the particular fluorescent color of that dye or ink. Itis known, for example, in the postage meter art to provide a redfluorescent ink for machine reading of processed mail.

It is therefore desirable to provide a thermal transfer ribbon having afluorescent ink layer thereon so that items such as tickets, tags,labels, postage imprints and the like can be imprinted with indicia suchas alphanumerics, bar code, slogans etc., by the use of such fluorescentthermal transfer ribbon. However, known prior art methods used for thepreparation of fluorescent inks generally use a technique that employs adispersion of resins and dyes. This type of technique has the followingdisadvantages: (1) It produces an ink with an inhomogeneous dyedistribution. (2) It produces an ink having a large dye particle size(3-30 m) and a broad particle size distribution. (3) It also produces anink that prints a fluorescent image having a weak intensity offluorescence and, in general, a short life time of fluorescence.

In U.S. Pat. No. 4,172,064, there is disclosed an aqueous copolymercoating system adapted for forming abrasionresistant coatings usingeither printing or coating processes. The copolymer employed in thecoating system includes: (1) a four component (monomer) copolymercomprising: (1) an alkyl methacrylate, (2) an alkyl acrylate, (3)unsaturated nitrile, and (4) unsaturated organic acid; (b) at least onecoalescing agent for the ether-alcohol types; (3) at least onesurfactant agent which may be either of the substituted polyethernon-ionic type or one of a group of selected anionic agents; and (d) oneor more additives as may be necessary to impart color, control foam, andprevent mildew and/or fungus attack. Basically, this patent is concernedwith printing ink copolymers and has no disclosure or suggestion of theidea of a fluorescent coating or printing an indicia which isfluorescent. Furthermore, unlike the present invention, the processdescribed by this patent (i) does not involve a chamical reactionbetween the dyes and monomers, i.e., a chemical bonding between dye andbasic monomer resulting in stronger intensity and longer lifetime offluorescence, (ii) does not treat a fluorescent dye with an acid monomerto put the dye in acidic form followed by treatment with a basic monomerand (iii) does not describe a fluorescent dye which is incorporated inthe monomers (describes a dye dispersed in an emulsion medium).

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved method for the preparation of a fluorescent ink layer for afluorescent thermal transfer sheet that is substantially devoid of theabove-noted disadvantages.

Another object of the present invention is to provide a method for thepreparation of an improved fluorescent ink layer which when used tomanufacture a fluorescent thermal transfer sheet used in printing,results in a relatively high intensity of fluorescence and a relativelylong lifetime of the fluorescent dyes.

A further object of the present invention is to provide a method for thepreparation of a fluorescent ink layer for a fluorescent thermaltransfer sheet which employs an emulsion polymerization process wherebya homogeneous distribution of the dyes in the resins is obtained.

A further object of the present invention is to provide a method for thepreparation of a fluorescent ink layer for a fluorescent thermaltransfer sheet wherein there is a chemical bonding between thefluorecent dyes and resins which improves the overall fluorescentlifetime of the dyes.

Still another object of the present invention is to provide a method forthe preparation of a fluorescent ink layer for a fluorescent thermaltransfer sheet wherein an acid monomer is first added to the dye toassist the dye to react and form an acidic group on the dye structurewhich subsequently assists the reaction of the dye with a basic monomer,thereby helping to increase the overall intensity of the fluorescence.

It is still another object of the present invention to provide a methodfor the preparation of a fluorescent ink layer for a fluorescent thermaltransfer sheet which provides for the adjustment of certain propertiesof the ink layer such as tackiness, general coating characteristics,thermal transfer temperature, stability of the emulsion, etc.

Still another object of this invention is to provide a method for thepreparation of a fluorescent ink layer for a fluorescent thermaltransfer sheet which additionally provides for adding such materials as,for example, a charge modifier to improve the surface contact with plainpaper and a cross linking agent to increase the stability of the printedimage.

The foregoing objects and others are accomplished in accordance with thepresent invention by providing a method for the preparation of afluorescent ink layer for a fluorescent thermal transfer sheetcomprising the following steps: First, a solution is formed of a mixturecomprising at least one acidic monomer, at least one basic monomer andat least one fluorescent dye. An emulsion of this solution is formed andthe emulsion is polymerized. The emulsion is actually a neutralizedemulsion that is formed by (1) mixing together at least one acidicmonomer and at least one fluorescent dye; (2) adding at least one basicmonomer to the mixture of the acidic monomer(s) and fluorescent dye(s),and then (3) adding an emulsifier to this mixture to form an emulsionwhich is subsequently polymerized.

In accordance with the preferred features of the method of thisinvention, a sufficient amount of one or more basic monomers is added tothe fluorescent dye(s) for the purpose of chemically reacting with thedye(s) (chemically bonding of the dye and basic monomer). Any excessbasic monomer (or unreacted basic monomer) will then chemically reactwith the subsequently added acid monomer(s) to form an ester monomer.The express purpose of adding the acid monomer is to have the dye reactand form an acidic group (COOH) on the dye structure which assists thereaction of the dye with the excess basic monomer. In accordance withthe preferred features of the method of the present invention, the acidmonomer(s) reacts with the basic monomer(s) to increase the intensity ofthe fluorescence and the overally lifetime of the fluorescent image.Thus, not only does the fluorescent ink layer obtain a very highintensity of fluorescence, but there is produced an extremely stablefluorescence under either ultraviolet or regular light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the method and resulting fluorescent ink layercomposition as defined by the present invention, machine readabletickets, tags, labels, postage imprints and the like can be providedwith a fluorescent image that can be read visually or by a number ofexisting machines that can be used for reading fluorescent ink imprintedinformation.

In accordance with the features of the present invention, the methodinvolves the following general steps: (1) First, there is the step ofmixing an emulsifier with water (preferably distilled water) at aboutroom temperature. Various types of ionic and non-ionic emulsifiers canbe used such as, for example, Triton X-200, Triton X-301, Triton X-305,Triton X-405, Triton Gr-5, Triton QS-44, Triton CF-32, Aerosol A-103 andAerosol A-102. (2) Second, in a separate container one or more acidicmonomers are mixed with one or more fluorescent dyes at about roomtemperature. In accordance with the preferred features of the presentinvention, about 2 to 5 times the ratio of acid monomer(s) tofluorescent dye(s) is used (2:1 to 5:1). Stirring is performed for apreferred period of about 5 to 30 minutes. Preferred acid monomersinclude an acid monomer having the general formula: ##STR1## where R₁ isH, CH₃ and R₂ is COOH, R₃ COOH wherein R₃ is C₁ -C₈. Examples of theseacid monomers include acrylic acid, maleic acid and p-vinyl benzoicacid.

The preferred fluorescent dyes useful in the method of the presentinvention are chosen based upon the fluorescent color that they exhibitand are preferably aromatic organic dyes such as Rhodamine Bx, RhodamineB, Phthalocyamine, Alkali Blue G, Phthalocyamine, Rhodamine 7G,Rhodamine FB, Rhodamine S, Rhodamine 6 GDN, Rhodamine 5G, Bright Yellow3G, Tteramethyl Rhodamine, Isothiocyanate, Rhodamine FG, Rhodamine F4G,Fanal Pink D, Fanal Violet D, Flexo Yellow 110, Lumogen Yellow D,Fluorol Green gold, Fluorol Yellow and Thermoplast F-Orange (3) In thethird step, one or more basic monomers are added to the acidicmonomer--fluorescent dye mixture, and the entire mixture is stirred atroom temperature for about 10 to 30 minutes. Basically, the amount(moles) of basic monomer that is added to the mixture is equal to orgreater than the amount (moles) of the combined amount of acidic monomerand dye.

The preferred basic monomers used are those having the general formula:##STR2## wherein R₄ is H, CH₃ and R₅ is OH, R₆ OH wherein R₆ is C₁ -C₈.Examples of such basic monomers include hydroxyl ethyl methacrylate,hydroxyl methyl methacrylate, hydroxyl prophyl methacrylate hydroxylethyl acrylate, hydroxyl methyl acrylate, hydroxyl propyl acrylate,eugenol and vinyl alcohol.

(4) Thereafter, the emulsifier is added to the monomer--fluorescent dyecombination to create an emulsion. Basically, this is done by stirringthe ingredients for a period ranging from about 10 minutes to about 30minutes at about 200 to 400 rpm to form a homogeneous emulsion

(5) One of the additional features in accordance with the method of thepresent invention involves including additional monomers to the emulsionwhen it is desired to provide to the ink layer of the fluorescentthermal transfer sheet improved properties of heat transfer and surfaceenergy. Adjusting the heat transfer properties is related to the energyrequirements of the thermal print head that will eventually be used withthe transfer sheet. Adjusting the surface energy is related to thesurface of the substrate that will be printed on, e.g., paper, plasticfilm, etc. Examples of the preferred additional monomers that can beadded to the emulsion to accomplish this result include vinyl monomerssuch as, for example, styrene, u-methyl styrene, vinyl toluene, methylmethacrylate, butyl acrylate, ethyl acrylate, propyl acrylateacrylnitrile and vinyl acetate.

At this point in the method the total percentage by weight of acidicmonomers, basic monomers, other monomers and fluorescent dyes in thetotal emulsified mixture is as follows: acidic monomers 20-40 percent,fluorescent dyes 1-10 percent, basic monomers 30-50 percent, other vinylmonomers 0-50 percent;

(6) The next step in the process is the polymerization of the emulsion.In accordance with the preferred embodiments of the present invention,the emulsion can be polymerized at room or at elevated temperatures by(i) adding an initiator with or without a reducing agent to theemulsion, or (ii) by just heating the emulsion at a temperature of about60° to 70° C. and stirring for about 5 hours. Examples of the optionalreducing agents which can be used include sulfite compounds such assodium metabisulfite or sodium thiosulfite which basically acceleratethe polymerization process. Examples of initiators which are used toinitiate the polymerization process include persulfates and peroxidessuch as potassium persulfate, ammonium persulfate, benzoyl peroxide andAlBN.

(7) Thereafter the solution is filtered through a material such ascheese cloth, and the fluorescent material is coated onto a propersupport substrate. In accordance with the preferred features of thepresent invention, various types of known prior art substrates can beused including Mylar, condenser paper and other polyesters andconductive polyurethanes. Of these, two substrates that are mostcommonly used include Mylar and special condenser paper. In accordancewith the features of the present invention, Mylar substrates arepreferred. The Mylar (from DuPont) can range in thickness from about 5to 10 microns.

There are several other ingredients that can optionally be added duringthe process to achieve certain desired end results. For example,molecular weight modifiers can be added for the purpose of decreasingthe molecular weight which results in decreasing the transfertemperature of the fluorescent coating. These modifiers could includesulfur containing compounds such as, for example, n-octyl mercaptan andn-dodecyl mercaptan. For the purpose of stablizing the emulsion and alsoimproving transfer properties, charge modifiers can be added. Examplesof this type of material include quartery ammonium salts such as, forexample, methacrylamidopropyl trimethyl ammonium chloride and2-trimethylammonium ethyl methacrylic chloride. To improve the overallfilming or coating characteristics of the fluorescent material aplasticizer in the form of an ester or polymer can be added. Examples ofthose plasticizers which are particularly suitable for the presentinvention include polypropylene glycol, tricresyl phosphate, dioctylphthalate, trioctyl phosphate, dioctyl sebacate, dibutyl phthalate,dibutyl sebacate and tributhyl phosphate. To stabilize the image that istransferred, a cross linking agent formed of an organic acid or ananhydride can be added. Examples of such cross linking agents includepolyethylene maleic anhydride, oxalic acid, malonic acid, adipic acid,fumaric acid, acetic anhydride, fuccinic anhydride and maleic anhydride.A general example of the procedure that is followed in performing apreferred method in accordance with the present invention for preparinga fluorescent thermal transfer sheet by monomer polymerization is asfollows:

It is to be noted that both in the general example and the examplesdescribed below any percentage figure listed is weight percent unlessotherwise stated.

An amount of emulsifier ranging from about 5 to 15% is added into aresin reaction vessel which contains distilled or deionized water. In aseparate container, about 0.5 to 5% of fluorescent dye(s), 2 to 20% ofacidic vinyl monomer(s) and 4 to 30% of basic vinyl monomer(s) are mixedtogether for a preferred period of about 5 to 30 minutes for the purposeof insuring the incorporation of the fluorescent dye(s) into themonomer(s). Thereafter, about 30 to 70% of additional vinyl monomer(s),0 to 5% of charge modifier(s), 0 to 5% of plasticizer(s) and 0 to 5% ofmolecular weight modifier(s) are added into the container, and all ofthese ingredients are mixed together. This mixture is slowly added intothe reaction vessel during a preferred period of about 10 minutes to 60minutes under mechanical stirring conditions (a mechanical stirrerhaving a speed of about 200 rpm to 500 rpm). Inert gas is bubbledthrough the mixture for a period ranging from about 10 to 30 minutes.0.1 to 5% of an initiator is then slowly added into the reaction vesselduring a period ranging from about 5 to 20 minutes. With or without theaddition of one or more reducing agents (in an amount ranging up toabout 5%), the reaction mixture is heated to a temperture ranging fromabout 4° C. to 90° C. for a period ranging from about 2 to 6 hours toinitiate and complete the polymerization step. From about up to 5% ofextra initiators and/or reduction agents is added to the mixture tocomplete the reaction during the end of the polymerization process. Thefinal product obtained by this procedure is then preferably mixed with alow molecular weight polyethylene emulsion and/or polyester, and coatedonto a substrate such as Mylar or condensed paper. The coated film isthen dried and can be supercalendered to insure the smoothness of thecoating surface. The following Examples are exemplary of the inventionand should not be considered limiting.

EXAMPLE 1 (ONE STEP MONOMER ADDITION METHOD)

50 ml of Triton X-305 (70% solid content from Rohmn and Haas Company)was transferred to a one liter, four-necked resin reaction vessel whichcontained 270 ml of dionized water. The acqueous solution wascontinuously stirred and bubbled with nitrogen gas. A 150 ml flask wasused to mix one gram of Rhodamine 6 GDN and 7 ml of acrylic acid. Afterstirring the mixture for 10 minutes, 13 ml of hydroxyethyl methacrylatewas added, and the mixture was stirred for 15 minutes. A monomer mixturecombining 80 ml of styrene, 25 ml of butylacrylate, 3 ml ofmethacrylamino propyl trimethyl ammonium chloride, 2 ml dodecylmercaptan and 1 ml dioctyl phthalate was mixed with the dye mixture. Theresulting mixture was then transferred to the resin vessel within a 60minute period through a drop regulator during stirring. The monomeremulsion was thus formed. An initiator mixture was formed with 4 gramsof potassium persulfate, 10 ml of water and 1 ml of Triton X-305 whichwas slowly added into the monomer emulsion to initiate thepolymerization. A reducing agent comprised of 5 grams of sodiummetabisulfite in 20 ml of water was added to the emulsion to acceleratethe reaction. The reaction was completed after about 5 hours ofcontinuously stirring the mixture and bubbling it with nitrogen. 50 mlof the final product was used and added to 30 ml of low molecular weightpolyethylene (Poly emulsion 656 A25, from Chemical Corp.) and 5 ml ofhigh molecular weight polyethlene (Poly emulsion 2-67 A, from ChemicalCorp.) for the subsequent coating of the fluorescent material onto Mylarfilm (from DuPont). Several coating methods including doctor bladecoating, gravure coating, kiss coating and rod coating were used toobtain the fluorescent thermal transfer film on the Mylar substrate.Good thermal transfer properties were found by developing an imagethrough a facsimile thermal printing head (Pitney Bowes Model 8400facsimile). The fluorescence was strong and stable without fading underexposure to ultraviolet light for an extended period of time.

EXAMPLE 2 (TWO STEP MONOMER ADDITION METHOD).

An amount of 80 ml of Triton X-200 (28% solid content from Rohmn andHaas Company) was added into a one liter, 4-necked reaction vessel whichcontained 400 ml of dionized water. The acqueous solution wascontinuously mechanically stirred at 300 rpm and bubbled through withnitrogen gas. A 100 ml flask was used to prepare the monomer mixture.Two grams of Rhodamine 6 GDN (from BASF Wyandotte Corp.) was mixed with8 ml of acrylate acid. After magnetically stirring the solution for 10minutes, 15 ml of 2-hydroethyl methacrylate was added. The mixture wasthen stirred for 15 minutes to form an emulsion. 25 ml styrene and 1 mlN-trimethyl ammonium propyl methacrylate chloride were added into themixture. The mixture was slowly added into the reaction vesselt hrough adrop regulator during a 30 minute period while continuously stirring.

In a separate flask, 60 ml of styrene and 40 ml of butylacrylate werecombined. This combination was then added into the reaction vesselduring a 30 minute period. The formation of a monomer emulsion was thencompleted. A mixture of 6 grams of ammonium persulfate, 20 ml ofdionized water and 4 ml of Triton X-200 were slowly added into themonomer emulsion to initiate the reaction. To begin and to acceleratethe polymerization process, 7 g of sodium metabisulfite, 20 ml ofdionized water and 3 ml of Triton X-200 was added. The final reactionmixture was kept at 60° C.-70° C. for 5 hours to complete thepolymerization process. A pink emulsion polymer having a solid contentof 27% was obtained. The emulsion was cooled while being stirred. Acombination of 50 ml of the emulsion polymer, 10 ml of high molecularweight polyethylene (Poly emulsion 2-67 A from Chemical Corp.) 50 ml oflow molecular weight polyethylene (Poly emulsion 656 A 25 from ChemicalCorp.) was used for coating the emulsion on 0.24 ml Mylar film (fromDuPont). Several coating methods including doctor blade coating, kissand rod coating were used to obtain the thermal transfer film on theMylar substrate. Good thermal transfer properties were found bydeveloping the image through a facsimile thermal printing head (PitneyBowes Model 8400). The fluorescent intensity was strong and stablewithout fading under exposure of ultraviolet light for an extendedperiod of time.

EXAMPLE 3

The same procedure as outlined in Example 1 was followed except theamount of each component was changed as follows:

    ______________________________________                                        Ingredients            Weight                                                 ______________________________________                                        H.sub.2 O              200      ml                                            Triton X-305           30       ml                                            acrylic acid           5        ml                                            Rhodamine 6GDN         1.5                                                    2-hydroxyl ethyl methacrylate                                                                        10       ml                                            styrene                50       ml                                            butylacrylate          15       ml                                            methacrylamindo-       5        ml                                            propyl trimethyl ammonium chloride                                            potassium persulfate   4        g                                             sodium metabisulfite   5        g                                             polyethylene maleic anhydride                                                                        5        g                                             ______________________________________                                    

EXAMPLE 4

The same procedure as outlined in Example 2 was followed except theamount of each ingredient was changed as follows:

    ______________________________________                                        Ingredients          Weight                                                   ______________________________________                                        H.sub.2 O            350       ml                                             Triton X-200         100       ml                                             acrylic acid         10        ml                                             Rhodamine 6GDN       2         g                                              2-hydroxyl methacrylate                                                                            18        ml                                             styrene              80        ml                                             butyl acrylate       40        ml                                             FLUOROL, Green Gold 084                                                                            0.2       g                                              ammonium persulfate  6         g                                              sodium metabisulfite 7         g                                              ______________________________________                                    

EXAMPLE 5

The same procedure as outlined in Example 2 was followed except theamount of each component was changed as follows:

    ______________________________________                                        Ingredients         Weight                                                    ______________________________________                                        H.sub.2 O           400        ml                                             Triton X-200        90         ml                                             acrylic acid        10         ml                                             Rhodamine           3          g                                              2-hydroxyethyl methacrylate                                                                       20         ml                                             styrene             90         ml                                             butyl acrylate      40         ml                                             ammonium persulfate 6          g                                              sodium metabisulfite                                                                              7          g                                              ______________________________________                                    

EXAMPLE 6

The same procedure as outlined in Example 2 was followed except theingredients were changed as follows:

    ______________________________________                                        Ingredients            Weight                                                 ______________________________________                                        H.sub.2 O              4600      ml                                           Triton X-200           900       ml                                           acrylic acid           120       ml                                           Rhodamine red 6GD      50        g                                            2-hydroxyethyl methacrylate                                                                          240       ml                                           styrene                160       ml                                           N--trimethyl ammonium methacrylate                                                                   7         ml                                           chloride                                                                      styrene                700       ml                                           butyl acrylate         430       ml                                           acrylic acid           50        ml                                           ammonium persulfate    40        g                                            H.sub.2 O              200       ml                                           Triton X-200           40        ml                                           sodium metabisulfite   50        g                                            H.sub.2 O              200       ml                                           Triton X-200           30        ml                                           ______________________________________                                    

EXAMPLE 7

The same procedure as outlined in Example 2 was followed except a 12 1resin reaction flask was used and the following ingredients was used:

    ______________________________________                                        Ingredients            Weight                                                 ______________________________________                                        H.sub.2 O              4600      ml                                           Triton X-200           900       ml                                           acrylic acid           120       ml                                           Rhodamine 6GD          50        g                                            2-hydroxyethyl methacrylate                                                                          240       ml                                           styrene                160       ml                                           N--trimethyl ammonium methacrylate                                                                   12        ml                                           chloride                                                                      styrene                700       ml                                           butyl acrylate         600       ml                                           acrylic acid           50        ml                                           ammonium persulfate    45        g                                            H.sub.2 O              200       ml                                           Triton X-200           40        ml                                           sodium metabisulfite   50        g                                            H.sub.2 O              200       ml                                           Triton X-200           40        ml                                           ______________________________________                                    

EXAMPLE 8

The same procedure as outlined in Example 2 was followed except a 12 1resin reaction flask was used and the following ingredients was used:

    ______________________________________                                        Ingredients         Weight                                                    ______________________________________                                        H.sub.2 O           4600       ml                                             Triton X-200        950        ml                                             acrylic acid        100        ml                                             Rhodamine 6GD       35         g                                              2-hydroxyethyl methacrylate                                                                       200        ml                                             styrene             220        ml                                             styrene             700        ml                                             butyl acrylate      450        ml                                             ammonium persulfate 68         g                                              H.sub.2 O           220        ml                                             Triton X-200        45         ml                                             sodium metabisulfite                                                                              80         g                                              H.sub.2 O           200        ml                                             Triton X-200        35         ml                                             ______________________________________                                    

EXAMPLE 9

The same procedure as outlined in Example 2 was followed except theingredients were changed as follows:

    ______________________________________                                        Ingredients         Weight                                                    ______________________________________                                        H.sub.2 O           700        ml                                             Triton X-200        200        ml                                             acrylic acid        20         ml                                             Basonyl red 485     3          g                                              Basonyl red 540     1.5        g                                              2-hydroxyl methacrylate                                                                           37         ml                                             N--trimethyl ammonium                                                                             2          ml                                             propyl methacrylate chloride                                                  styrene             300        ml                                             ammonium persulfate 15         g                                              sodium bisulfite    17         g                                              ______________________________________                                    

In all of Examples 3 through 9 good results regarding fluorescence wereobtained by following the described procedure and the listedingredients.

What is claimed is:
 1. A method for the preparation of a fluorescentthermal transfer sheet comprising:(a) forming a solution of a mixturecomprising at least one acidic monomer having the basic formula:##STR3## where R₁ =H, CH₃ and R₂ is COOH, R₃ COOH wherein R₃ is C₁ -C₈,and at least one basic monomer having the basic formula: ##STR4##wherein R₄ is H, CH₃ and R₅ is OH, R₆ OH wherein R₆ is C₁ -C₈ and atleast one fluorescent dye; (b) forming an emulsion of the solutionformed in step (a); (c) adding at least one vinyl monomer to theemulsified solution of step (b); (d) adding a reducing agent to aninitiator (e) polymerizing the solution of step (c) at room temperatureby adding the initiator from step (d) to said neutralized emulsion; and(f) coating the polymerized mixture from step (e) onto a polyester film.2. A method according to claim 1 wherein said polyester film is Mylar.3. A method according to claims 1 wherein the number moles of said basicmonomer is equal to or greater than the total number of moles of thecombination of said fluorescent dye and said acidic monomer.
 4. A methodfor forming a fluorescent thermal transfer sheet, comprising:(a) forminga neutralized emulsion from a mixture comprising at least one acidicmonomer and at least one fluorescent dye by (i) mixing together at leastone acidic monomer having the basic formula: ##STR5## where R₁ ═H, CH₃and R₂ is COOH, R₃ COOH wherein R₃ is C₁ -C₈ and at least onefluorescent dye; (ii) adding at least one basic monomer to the mixtureof step (i), the basic monomer having the basic formula: ##STR6##wherein R₄ is H, CH₃ and R₅ is OH, R₆ OH wherein R₆ is C₁ -C₈ ; and(iii) adding an emulsifier to the mixture of step (ii) to form anemulsion; (b) polymerizing said neutralized emulsion of step (a); and(c) coating said polymerized mixture onto a support member.
 5. A methodaccording to claim 4 wherein said support member is a polyester film. 6.A method according to claim 5 wherein said polyester film is Mylar.
 7. Afluorescent thermal transfer sheet prepared by the method as describedin claim 4.